The present invention is a process for the preparation of hydrolyzable .beta.-cyanoalkylsilanes. More particularly, this invention relates to the catalytic addition of trichlorosilane to .alpha.,.beta.-unsaturated olefinic nitriles to form .beta.-cyanoalkylsilanes. The present process employs a catalyst comprising a ruthenium compound. The preferred catalyst for the present process is a ruthenium compound having at least one tertiary phosphine ligand.
Beta-cyanoalkylsilanes having hydrolyzable chlorines bonded to the silicon atom are useful for the production of polyorganosiloxanes containing the .beta.-cyanoalkyl substituent. The silicon-bonded .beta.-cyanoalkyl substituent is extremely resistant to hydrolysis and cleavage under hot, humid conditions and imparts these characteristics to the polyorganosiloxane of which they are a substituent. The presence of the silicon bonded .beta.-cyanoalkyl substituent on polyorganosiloxanes also tends to stabilize the polyorganosiloxanes against swelling induced by liquid hydrocarbons. In addition, .beta.-cyanoalkylsilanes having hydrolyzable chlorines are useful reactive intermediates for forming, for example, gamma-organoaminotrialkoxysilanes which are useful as surface treating agents.
It is known that when trichlorosilane is contacted with an olefinic nitrile, as exemplified by acrylonitrile, at a sufficient temperature a mixture of .alpha.-cyanoalkylsilanes and .beta.-cyanoalkylsilanes is formed. In addition other reactions such as the formation of both silicon and non-silicon-containing complexes, homopolymerization of the starting nitrile, and the disproportionation of the starting silane can occur. The .alpha.-cyanoalkylsilanes are hydrolytically unstable. Therefore, the .beta.-cyanoalkylsilanes generally have more commercial utility than the .alpha.-cyanoalkylsilanes and processes for producing high yields of .beta.-cyanoalkysilanes are desirable.
A number of catalyst have been reported useful in the preparation of .beta.-cyanoalkylsilanes. Saam, U.S. Pat. No. 2,860,153, issued Nov. 11. 1958. describe a process for preparing .beta.-cyanoethyltrichlorosilane by heating at a temperature less than 150.degree. C. a mixture of acrylonitrile and trichlorosilane with a catalytic amount of an amine.
Jex et al., U.S. Pat. No. 2,906,764, issued Sep. 29, 1959, describe a process where organosilanes having at least one hydrogen and one hydrolyzable group bonded to silicon are reacted with an alkene nitrile in the presence of a diarylamine catalyst to produce preferentially .beta.-cyanoalkylsilanes.
Jex et al., U.S. Pat. No. 2.907.784, issued Oct. 6, 1959, describe a process where organosilanes having at least one hydrogen and one hydrolyzable group bonded to silicon are reacted with an alkene nitrile in the presence of a trihydrocarbylphosphine catalyst to produce preferentially .beta.-cyanoalkylsilanes.
Bluestein, U.S. Pat. No. 2.971.970, issued Feb. 14, 1961, describes a multiple component catalyst system useful for the production of .beta.-cyanoalkylsilanes by the reaction of alkene nitriles with organosilanes having at least one hydrogen. The catalyst comprises a cuprous compound, a diamine, and a trialkylamine.
Rajkumar et al., Organometallics 8:549 (1989), describe a two-component catalyst effective in hydrosilation of acrylonitrile leading to the .beta.-addition to the double bond of the acrylonitrile. The catalysts consist of cuprous oxide and tetramethylethylenediamine.
Bank, U.S. Pat. No. 5,126.468, issued Jun. 30, 1992, describes a process for the preparation of hydrolyzable .beta.-cyanoalkylsilanes. The process employs novel catalysts comprising a diamine and non-activated copper, selected inorganic copper compounds, and di-coordinate organic copper compounds.
Bank, U.S. Pat. No. 5,126,469, issued Jun. 30, 1992, describes a process for the preparation of hydrolyzable .beta.-cyanoalkylsilanes. The process employs a catalyst comprising a diamine and supported copper or a supported copper compound.